How can I make a one time payment with a card?

Hello scootaluv,

You started from a great resource to add a payment to your Apple ID. Add a payment method to your Apple ID. Once the steps in the article are complete you can add and pay for your subscription.

You can also find additional ways to subscribe to Apple Music depending on the device you are using here: Join Apple Music on your iPhone, iPad, iPod touch, Mac, or PC

The steps below found in the article here also have details on payment method order. How apps, content, and subscriptions from Apple are billed

"Which payment method is charged?

When you buy items or pay for subscriptions, Apple attempts to charge your payment methods in this order:

1. Apple attempts to use your Apple Account balance to cover the full amount.
2. If you don't have Apple Account balance or you don't have enough to cover the full amount, Apple attempts to charge your primary payment method. The primary payment method is at the top of the list in Settings on your iPhone. You can control which payment method is at the top of the list.
3. If there's a problem with the primary payment method, or if the primary payment method can't be charged for the full remaining amount, Apple attempts to charge your other payment methods in order from top to bottom. If none of them can be charged, Apple might try again."

Hope the information helps with adding your payment method and how items are charged.

Cheers.